Thank you
very much for the detailed steps!
But, unfortunately I have no clue what's going on. Your VM recipe is crystal clear (except maybe your vRAM being a tad low at 16 MB). Your logs show absolutely nothing out of the ordinary. Here's actually what happens between when you plug in the USB drive and when you unplug it:
00:01:04.181081 VUSB: Attached '00007f10c0c65de0[proxy 0951:1666]' to port 1
00:01:04.181704 EHCI: USB Operational
00:01:34.255532 VUSB: Detached '00007f10c0c65de0[proxy 0951:1666]' from port 1
Nothing. Absolutely nothing. In those 30 sec I suspect that you tried to type unsuccessfully, ejected the USB, tried to type unsuccessfully, removed the USB and after that everything keyboard-wise returned to normal.
The only thing I can think of before I send you to the
bugtracker, would be to switch from USB2 to USB3. See if that makes a change.
Also, out of curiosity, are you using a hub to attach the USB drive or is it own port? If on a hub, try a stand-alone port or a different port altogether.